Micro-relay

ABSTRACT

A microstructure relay is provided, having a body that includes upper and lower portions. The lower portion is formed from a substrate, and the upper portion is formed on the substrate to avoid bonding of the lower portion to the upper portion. A support member is fixed to the body at a first end of the support member to form a cantilever, wherein an upper surface of the support member and a lower surface of the upper portion of the body form a cavity. A first contact region is located on the upper surface at a second end of the support member. The first contact region comprises a first contact, wherein pivoting the support member toward the lower surface causes the first contact to be electrically coupled to a counter contact.

FIELD OF THE INVENTION

The invention relates generally to microstructures and particularly torelays and switches or valves formed from microstructures.

BACKGROUND OF THE INVENTION

Electrical relays are widely used in various applications. Suchapplications include, for example, the selection of different electricalpaths or the opening or closing of an electrical circuit.

Typically, relays include a coil and mechanical components for engagingand disengaging a pair of contacts. Upon energizing the coil, anelectromagnetic field is generated to engage the contacts, forming theelectrical connection.

There is now a demand for the miniaturization of consumer goods (e.g.,electronic and telecommunication products) or electronic equipments(e.g., automated test equipment), which creates a corresponding need toreduce the size of relays. However, conventional electromechanicalrelays do not lend easily to miniaturization. For example, there is alimit as to the size of coils that can be reduced. Such limitationsreduce the extent of miniaturization of products using relays.

The above discussion evidences a need to provide a relay design thatallows for further miniaturization.

DESCRIPTION OF THE DRAWINGS

FIGS. 1a-1 b are cross-sectional and plan views of a relay in accordancewith one embodiment of the invention;

FIGS. 2a-2 b are cross-sectional and plan views of a relay in accordancewith another embodiment of the invention;

FIGS. 3-8 are three-dimensional views depicting a process of fabricatinga relay in accordance with one embodiment of the invention;

FIGS. 9-10 are three-dimensional views depicting an alternative processof fabricating a relay; and

FIGS. 11-12 are three-dimensional views depicting another process offabricating a relay.

SUMMARY OF THE INVENTION

The invention relates to a microstructure relay. The relay comprises abody having upper and lower portions. A support member having a firstend fixed to the body to form a cantilever is provided. The uppersurface of the support member and a lower surface of the upper portionof the body form a cavity. A first contact region is located on theupper surface at a second end of the support member. The first contactregion includes a first contact that is electrically coupled to a secondcontact when the support member is moved upward toward the lowersurface.

In accordance with one embodiment of the invention, the upper portion ofthe body is formed on the lower portion of the body. This requires onlya single substrate to fabricate the relay, avoiding the need to bondupper and lower portions of the relay together.

In accordance with another embodiment of the invention, the relaycomprises an s-shaped support member to provide over-travel. First andsecond stress layers are used to form the s-shape support member. Thefirst stress layer induces compressive stress to cause the supportmember to bend away form the upper portion of the relay, and a secondlayer is provided to induce the first contact region to bend in theopposite direction toward the upper portion of the relay. The firststress layer can be patterned to be on the support member except in thefirst contact region. The stress layers, in one embodiment, comprisehigh temperature materials formed using semiconductor processingtechniques.

A method for fabricating microstructures is provided. The methodincludes the use of electrochemical etching to form microstructures.Electrochemical etching relies on an etch stop which, for example, maybe a p-n junction. The electrochemical etch etches, for example, p-dopedportion or region and stops on n-doped region. In one embodiment, aheavily doped p-type region is used. The use of a heavily doped p-typeregion enables the etch to form holes or slots having lateral dimensionsless than 250 μm.

DESCRIPTION OF THE INVENTION

The invention relates to the fabrication of microstructures. Inparticular, the invention relates to forming relays frommicrostructures. The use of microstructures enables the fabrication ofminiature relays.

FIGS. 1a-b are cross-sectional and plan views, respectively, of amicro-relay in accordance with one embodiment of the invention. Asshown, the relay comprises a body 110. The body includes a supportmember 160. The support member is supported at a first end 163 by thebody, forming a cantilever. A first contact region 133 is provided atabout a second end 165 of the support member. The first contact regioncomprises a first contact 131.

A gap separates a top surface 168 of the support member and a surface109 of the body, forming a cavity 121. The cavity allows the supportmember to pivot about the first end 163. The surface 109 comprises acontact region 134 on which a second contact 130 is provided. The secondcontact is usually referred to as the counter contact. The first andsecond contacts are positioned such that they contact each other whenthe support member is pivoted upward toward surface 109. The dimensionsof the contacts depend on design parameters and can be varied asrequired. Typically, the height of the contacts is about 2-10 microns(μm).

An electrostatic force is used to move or pivot the support membertoward surface 109 to engage the first and second contacts. The relayincorporates the use of electrodes having opposite charges or oppositedipole layers applied thereto to generate the electrostatic force.

In accordance with one embodiment of the invention, a first electrode141 is located on the surface 168 of the support member and a secondelectrode 140 is located on the surface 109 of the body. The electrodesare isolated from the contacts. The first and second electrodes, asshown, are aligned with each other to produce an electrostatic forcewhen opposite charges are applied to the electrodes. A dielectric layer145 is provided either on the first or the second electrode to preventshorting when the support member is moved upward toward surface 109.Providing a dielectric layer on both electrodes is also useful.

In effect, the electrodes and dielectric layer form a capacitor forgenerating the electrostatic force. The amount of electrostatic forcegenerated depends on, for example, the surface area of the electrodes,the voltage applied to the electrodes (pull-in voltage), and thedistance between the electrodes. The applied voltage needed to create asufficient electrostatic force depends on design parameters such as thestiffness of the support member and the contact force desired.

In one embodiment, the body includes upper and lower portions 105 and106. The lower portion 106 preferably comprises silicon. Othercrystalline materials such as gallium arsenide are also useful.Materials such as quartz, ceramics, glass, silicate glass such asborosilicate glass, Pyrex®, or other materials that can provide supportfor the relay components can also be used. The upper portion 105, in oneembodiment, comprises nickel or a nickel alloy such as nickel-iron.Other materials, including gold, alloys, plastic, epoxy, and materialsthat can adequately support the relay components as needed, can also beused.

In accordance with one embodiment of the invention, the upper portion isformed or deposited on the lower portion. This advantageously avoids theneed to bond the upper and lower portions together as required byconventional two wafer approaches, improving reliability and loweringmanufacturing cost.

In the upper portion, surface 109 is provided on which the secondcontact 130 is located. The second contact is formed in a second contactregion 134 on surface 109. As shown, a surface 108 in the second contactregion is recessed from surface 109 to produce a separate contact regionfor the contact. A second contact region that is not recessed fromsurface 109 can also be used. The contact comprises a conductivematerial. The contact material should have low contact resistance, goodthermal conductance, and hardness to resist sticking over the life timeof the relay. Other desirable characteristics of the contact materialincludes high resistance against light arcing, high light arcingvoltage, low stress, and low or no cold welding effects. In oneembodiment, the contact comprises gold. For example, including gold suchas gold-palladium, gold-nickel, and gold-cobalt or alloys includingsilver are also useful. Other conductive materials that provide goodcontact characteristics are also useful to form the contact.

Supported by the body at the first end 163 is the support member 160.The first contact region 133 comprising the first contact 131 is locatedat about the second end 165 of the support member. It is not necessaryto use the same material to form both the first and second contacts.When the support member is moved upward, the contacts make contact witheach other.

In one embodiment, the support member is part of the lower portion ofthe body. Such a support member comprises the same material as the lowerportion of the body. In a preferred embodiment, the support membercomprises single crystalline silicon. Other single crystalline materialsare also useful for forming the lower portion and support. Materialsthat comprise good spring characteristics such as low fatigue and creepare also useful.

Providing a support member that is not part of the lower portion of thebody is also useful. With such a design, materials which are differentfrom those comprising the lower portion of the body can be used for thesupport member. Materials that exhibit good spring characteristics areuseful to form the support member. In one embodiment, the support membercomprises polysilicon (poly). The poly can be deposited either as polyor as amorphous silicon and recrystallized to form poly. The use ofepitaxially grown single crystalline material to form the support memberis also useful. Nickel, nickel alloy such as nickel-iron, metals, ormetal alloys that show good spring characteristics can also be used toform the support member.

The second electrode 140 is provided on the surface 109 of the upperportion of the body, and the first electrode 141 is provided on thesurface 168 of the support member. The electrodes comprise a conductivematerial. Various conductive or semi-conductive materials can be used toform the electrodes. To simplify processing, the electrodes can beformed from the same material used to form the contacts. The thicknessof the electrodes is not critical. However, the first electrode shouldbe relatively thin to reduce the impact of mechanical stress induced bythe electrode on the support member. In one embodiment, the firstelectrode should be as thin as possible to minimize the stress on thesupport member. The electrodes are isolated or separated from thecontacts. The separation between the contact and electrodes depends ondesign requirements such as the insulation voltage between the feed andload circuits, and the maximum continuous driving voltage.

The dielectric layer 145, in one embodiment, is provided over the secondelectrode to provide isolation between the electrodes and othercomponents as needed. Providing the dielectric layer over the firstelectrode or on both electrodes is also useful. The thickness of thedielectric layer depends on the insulation characteristics of thematerial and design requirements such as, for example, the insulationvoltage between the feed and load circuits and maximum continuousdriving voltage.

The electrodes and contacts are provided with respective connections orreadouts 178 to contact pads 179. The exact configuration and locationof the pads and leadouts are not important. The contact pads to theelectrodes are coupled to voltage sources of opposite polarity, creatingthe drive circuit. The contact pads to the contacts are coupled toportions of the load circuit. When the contacts are not engaged, theload circuit is opened. Applying the oppositely charged voltages to theelectrodes generates an electrostatic force, causing the support memberto move upward. This engages the first and second contacts, closing theload circuit.

Illustratively, the first and second contacts are coupled to arespective portion of the load circuit. The leadout coupling the firstcontact to pad is provided over the first electrode. To isolate theelectrode from the lead out, the first electrode is divided into twoportions 141 a and 141 b. As such, leadouts are provided to couple theelectrodes to a common pad. Alternatively, a dielectric layer can beprovided under the lead out to provide electrical isolation between theelectrode and the lead out.

In another embodiment, the first contact is not coupled to a portion ofthe load circuit. Instead, first and second counter contacts areprovided, coupling to respective portions of the load circuit. Therespective portions of the load circuit are electrically coupled whenthe support member is moved upward to make contact with first and secondcounter contacts. Such a design does not require a leadout and pad forthe first contact, eliminating the need to divide the first electrodeinto two portions or to provide a dielectric layer between the leadoutand electrode forming a bridge contact. Additional contacts oralternative contact configurations are also useful. For example,multiple sets of contacts can also be provided for driving a pluralityof load circuits.

A sufficiently high force between the contacts is desired in order tohave low contact resistance. The low contact resistance should bemaintained over the lifetime of the relay, in view of contact wear. Inone embodiment, the relay comprises an over-travel to produce highcontact force between the contacts. The over-travel is the distance thatone contact travels beyond the surface of the other contact in theabsence of the other contact when the support member is moved upward toengage the contacts. Ideally, the over-travel adequately maintains thehigh contact force to produce a low stable contact resistance over thelifetime of the relay. The amount of over-travel provided depends on,for example, the wear on the contact and contact characteristics. Theover-travel, for example, is about 5 μm. Other over-travel distances arealso useful.

In one embodiment, the over-travel is incorporated in the supportmember. The over-travel results from an s-shaped support member (asshown by the dotted lines). The s-shape is achieved by inducing the mainportion of the support member to deflect or bend about an axis in afirst direction and inducing the end 165 to bend in the oppositedirection. To create the s-shape, the main portion of the support memberis induced to deflect downward away from the surface 109 while the end165 is induced to bend upward toward the surface 109.

In one embodiment, over-travel is provided by inducing the main portionof the support member to deflect downward away from surface 109 whileinducing the first contact region to deflect in the opposite directionof the main portion. In a preferred embodiment, the first contact regionis isolated from remaining end portions 165 a and 165 b of the supportmember. Isolating the first contact region forms a cantilever within thesupport member. Such a design is advantageous as it increases thecontact force applied between the contacts.

In one embodiment, a first stress layer 180 is provided on the surface168 of the support member. The first stress layer induces a compressivestress on the support member, causing it to bend or arc downward awayfrom the first electrode. Preferably, the first stress layer induces anintrinsic compressive stress of the support member. The second stresslayer 181 is provided in the first contact region at about the secondend of the support member, inducing a tensile stress to cause the firstcontact region to arc upward toward the surface 109. Preferably, thesecond stress layer induces an intrinsic tensile stress on the firstcontact region of the support member. This combination of the tensileand compressive stresses creates the s-shaped support member. The amountof bending depends on the material and its thickness. The material andthickness of the stress-inducing layers are selected to create the shapethat produces the desired amount of over-travel.

In an alternative embodiment, the first stress-inducing layer isprovided on the surface 168 of the support member except in the firstcontact region. The first layer induces a compressive stress on thesupport member, causing it to bend or arc downward away from the firstelectrode. The second layer is provided in the first contact region atabout the second end of the support member, inducing a tensile stress tocause the first contact region to arc upward toward the surface 109.

The stress-inducing layers preferably comprise relatively hightemperature formed materials such as those used in semiconductorprocessing. Such materials include, for example, silicon oxide, siliconnitride, poly, and epitaxially grown silicon. The materials can be dopedor undoped.

The high temperature formed materials comprise stable mechanicalproperties (e.g., intrinsic stress, low fatigue and creep) and areunaffected by other lower temperature processes used in forming therelay. The stability and repeatability of high temperature formedmaterials provide an excellent stress-inducing layer, enabling thesupport member to maintain its shape over time and various a operatingtemperatures. This improves the reliability of the relay. Furthermore,the use of such materials reduce production cost.

Ad In one embodiment, the support member comprises silicon. The firststress-inducing layer comprises silicon oxide to induce compressivestress on the support member. Other materials that induce compressivestress on the support member, such as doped or undoped poly, are alsouseful. To induce tensile stress on the support member, the secondstress-inducing layer comprises silicon nitride (Si₃N₄). Other materialsthat induce tensile stress on the support member are also useful.

Alternatively, metals or other materials formed by lower temperatureprocesses to either induce compressive or tensile stress on the supportmember can also be used as stress-inducing layers.

As described, non-symmetrical material combinations having differentstresses at about the bending axis are used to induce bending of acomposite structure. The stress induced includes different components,such as intrinsic stress and stress due to thermal expansion. Thedifferent stress components can be affected by the thickness of thestress-inducing layer. Increasing or decreasing the thickness increasesor decreases the magnitude of the intrinsic stress component on thesupport member. The thermal component of stress, which depends on amaterial's thermal coefficient of expansion (TCE), is also affected bytemperature. The stress due to thermal expansion changes as thestress-inducing layer expands or contracts due to temperaturevariations.

In some applications, particular with devices that operate over a wideoperating temperature range, it may be desirable to have a supportmember that maintains a stable shape over the contemplated operatingtemperature range. A stable support member can be maintained over abroad temperature range by effectively reducing or minimizing thethermal component of stress. Different techniques can be employed toreduce the stress variations from TCE.

In one embodiment of the invention, variations of stress due to TCE isreduced or minimized by employing stress-inducing layers comprising TCEsthat are similar to that of the support member. Closely matching theTCEs of the different materials enables the support member to maintain astable shape over the relay's contemplated operating temperature range.

Alternatively, variations in the stress induced by the stress layer dueto thermal expansion can be avoided by using thinstress-inducing layers.Reducing the thickness of the stress layers decreases their thermalstress component. Using a thin stress layer may require the material tohaving a higher intrinsic stress component to produce the desiredbending on the support member.

In yet another embodiment, a compensation layer is used to reduce orminimize the effects of a mismatch between the TCEs of the differentlayers. In one embodiment, the compensation layer is provided in contactwith the stress-inducing layer. In one embodiment, the compensationlayer is provided between the support member and stress-inducing layer.The compensation layer comprises a TCE that is similar but opposite(compressive instead or tensile or vice-versa) to that of the stresslayer. Providing a compensation layer having the opposite TCE as the TCEof the stress-inducing layer cancels out the effects of the TCEmismatch.

In the case where the support member is not a part of the lower portionof the body, the compensation layer can be provided on the oppositesurface on which the stress-inducing layer is located. In oneembodiment, the compensation layer is provided on the lower surface ofthe support member while the stress-inducing layer is on the uppersurface of the support member. The compensation layer comprises a TCEthat is similar to that of the stress-inducing layer. Providing acompensation layer having a TCE that closely matches the TCE of thestress-inducing layer on the opposite surface of the support membercancels out effects of the TCE mismatch between the stress-inducinglayer and support member.

The intrinsic stress in the compensation layer should be much lower thanthe intrinsic stress in the stress layer in order to reduce or minimizecompensation layer's influence on the support member.

To ensure that the over-travel of the support member is not hindered, anover-travel region 170 can be provided on the surface 109. Theover-travel region is created by recessing a surface 171 from surface109. The over-travel region enables the upward bend of the supportmember not to be inhibited by the surface 109. The dimensions of theover-travel region should be sufficient to accommodate the over-travelof the support member. The surface area of the over-travel region shouldbe larger than the surface area of the over-travel portion of thesupport member. The depth or height of the over-travel region is, forexample, equal to the sum of the heights of the first and secondcontacts.

As shown from the plan view of FIG. 1b, the support member comprises acantilever which is somewhat rectangular in shape. Other shapes, such ascircular or elliptical shapes, are also useful. The size or surface areaof the support member can be designed to take into account the sizerequirements of the electrodes in order to generate the force needed tomove the support member. The surface area of the support member can be,for example, 1500 μm by 1200 μm.

FIGS. 2a-b are cross-sectional and plan views of an alternativeembodiment of the invention. As shown, the relay incorporates a dualsupport member design comprising first and second support members 260and 270. The use of dual support members advantageously avoids the needof a second stress layer (tensile stress inducing layer) to produce theover-travel. The relay comprises a body 210. The first support member260 is supported by the body at a first end 262, forming a cantilever.Likewise, the second support member comprises a cantilever having afirst end 272 supported by the body. The support members are effectivelyin about a same plane. A gap separates the support members and a surface209 of the body, forming a cavity 221.

In one embodiment, the body comprises lower and upper portions 205 and206. The lower portion comprises silicon. Other crystalline materialssuch as gallium arsenide are also useful. Materials such as quartz,ceramics, glass, silicate glass such as borosilicate glass, Pyrex®, ormaterials that can provide support for the relay components a can alsobe used. The upper portion 105, in one embodiment, comprises nickel.Other materials, including gold, plastic, epoxy, and materials that canadequately support the relay components as needed, can be used.

Providing a support member that is not part of the lower portion of thebody is also useful. With such a design, materials which are differentfrom those comprising the lower portion of the body can be used for thesupport member. Materials that exhibit good spring characteristics(e.g., low fatigue and creep) are useful for the support member. Asupport member comprising poly, for example, can be useful. The poly canbe deposited either as poly or as amorphous silicon and recrystallizedto form poly. The use of epitaxially grown single crystalline materialto form the support member is also useful. Nickel, nickel alloy such asnickel-iron, metals or other alloys that have the desiredcharacteristics can also be used to form the support member.

A first contact 231 is located at about a second end 265 of the firstsupport member, and a second contact 230 is located at about a secondend 275 of the second support member. The contacts are positioned suchthat when the first support member moves upward toward the surface 209,they come into contact with each other.

In accordance with one embodiment of the invention, the second contactis the counter contact, and the first contact is moved upward to contactthe second contact. The length of the second support member isrelatively short to provide sufficient stiffness in order to produce thedesired counter-force on the first contact when the contacts areengaged.

The first contact extends beyond the first support member to ensure thatcontact is made with the second contact when the second member is movedupward toward surface 209. In one embodiment, the portion of the contactthat extends beyond the first support member is in a different planewith respect to the portion of the contact on the support member. In oneembodiment, the portion of the contact that extends beyond the supportmember is in a plane elevated above the plane of the portion of thecontact on the support member. This provides for separation of thecontacts when they are not engaged.

A first electrode 241 is located on surface 268 of the first supportmember, and a second electrode 240 is located on surface 209. Adielectric layer 245 is provided over either the first or secondelectrode. Providing a dielectric layer over both electrodes is alsouseful. In one embodiment, the dielectric layer is provided over thesecond electrode. Upon the application of opposite charges to the firstand second electrodes, the first support member moves upward toward thesecond electrode to create electrical coupling between the contacts.

Over-travel can be incorporated into the relay design. In oneembodiment, over-travel is provided by arcing the first and secondmembers downward away from surface 209 (as depicted by the dottedlines). The downward bend is incorporated by inducing compressive stresson the support members. As previously described, compressive stress isinduced by the use of a compressive stress-inducing layer 281.

Providing an s-shaped first support member to produce over-travel isalso useful. The s-shaped support member is created using a compressiveand tensile stress-inducing layers as described in FIGS. 1a-b.

In one embodiment, an over-travel region 290 is provided. Theover-travel region ensures that there is a sufficient gap between thecounter contact 230 and end 265 to prevent obstructing over-travel ofthe support member 260.

FIGS. 3-8 show the process for forming a relay in accordance with oneembodiment of the invention. The figures provide a cross-section of a3-dimensional view of the process. The cross-section is taken along anaxis at about half of the support member. The other half of the supportmember is typically, but not necessarily, symmetrical with the half asshown.

In accordance with one embodiment of the invention, electrochemical etch(ECE) techniques are used to form the support member. ECE techniquesemploy the use of oppositely doped regions and the application of acharge. In one embodiment, the ECE etches the p-typed doped regions andpassivates on the n-doped regions. As such, the n-doped regionseffectively serve as an etch stop. Using ECE to etch the n-doped regionsinstead of the p-doped regions could also be useful.

Referring to FIGS. 3, a substrate 301 is provided. The substratepreferably comprises silicon such as a silicon wafer. Other crystallinesubstrates such as gallium arsenide are also useful. Substratescomprising materials such as quartz, ceramics, glass, silicate glasssuch as borosilicate glass (e.g. PYREX®), or materials that can providesupport for the relay components can also be used.

In one embodiment, an ECE etchant that is selective to the crystalorientation of the substrate is employed. The use of an etchant thatetches in certain crystal planes advantageously enables the use of wetetch chemistries to define the support member.

In one embodiment, KOH is employed as the ECE etchant to etch silicon.KOH preferably etches silicon in the 100 plane selective to the 111plane (i.e., a much higher etch rate in the 100 plane with respect toother planes). To accommodate the etch characteristics of the etchant,the substrate is oriented in the 100 plane. Other crystal orientationsmay also be useful.

The substrate includes a first doped region 305 comprising dopants of afirst type. In one embodiment, the first doped region comprises p-typedopants, such as boron (B). A second doped region 307 comprising dopantsof a second type is formed on the surface of the substrate. In oneembodiment, the second doped region comprises n-type dopants, such asarsenic (As) or phosphorus (P), in order to form an n-doped region.Using n-type dopants to form the first doped region and p-type dopantsto form the second doped region is also useful.

The pattern or design of the second doped region defines the shape ofthe support member 360. As shown, the n-doped region is in the shape ofa cantilever to serve as the support member. In one embodiment, thecantilever comprises edges that are perpendicular with respect to eachother. Other cantilever shapes are also useful. For example, edgeshaving angles other than 90° with respect to each other or curved edgesare also useful. The depth of the second doped region defines thethickness of the support member. A subsequent ECE process selectivelyremoves the first doped region 305 to form the support member.

The dimension of the support member determines its stiffness. Thestiffness of the support member should enable the contacts to disengageor release when the voltage applied to the electrodes drops below thespecified drop-out voltage and engage the contacts when the voltageapplied to the electrodes exceeds the specified pull-in voltage. Thedimension of the support member, for example, is about 1200 μm wide,1500 μm long, and 10 μm thick. Other dimensions are also useful,depending on design specifications such as the pull-in and drop-outvoltages.

In accordance with one embodiment of the invention, the first dopedregion comprises a heavily doped region, for example, a heavily p-doped(p+) region. In one embodiment, the p+ region comprises a dopantconcentration that results in a resistivity of about 50 mΩ*cm.

The use of a first doped region that is heavily doped provides animprovement over conventional ECE techniques, which use a lightly dopedregion. The lightly doped region results in a substrate having aresistivity of about 6-9 mΩ*cm. At such resistivity, ECE can only formholes or slots of greater than 250 μm. Increasing the dopantconcentration to decrease resistivity to less than 6 mΩ*cm enables theformation of holes or slots less than 250 μm. Increasing the dopantconcentration to result in a substrate having a resistivity of about 50mΩ*cm enables the formation of significantly smaller features, forexample, less than 60 μm, preferably about 30 μm. Smaller featuresadvantageously allow for smaller relay structures.

In one embodiment, a p-doped substrate having the desired dopantconcentration is used to provide the p-doped region. Alternatively,p-type dopants are implanted and/or diffused into the substrate to formthe p-doped region 305.

An n-doped region 307 is formed on the surface of the substrate. Then-doped region is formed by, for example, implanting dopants such as Asor P, into selected regions of the substrate. The dopant concentrationof the n-doped region should be sufficient to form a proper p-n junctionwith the p-doped region. Typically, the dopant concentration of then-doped region is about 10¹⁸-10²⁰ atoms/cm³. In one embodiment, a POCl₃source is used to selectively deposit P dopants into the substrate toform the n-doped region 307. A diffusion mask comprising, for example,silicon oxide (SiO₂) is used to protect certain regions of the substratefrom being diffused with dopants while allowing dopants to enter theunprotected regions of the substrate. Alternatively, the dopants can beselectively implanted into the substrate.

In one embodiment, a first contact region 368 in which a first contactis formed is defined at about an end 365 of the support member. Thefirst contact region, in one embodiment, forms a cantilever within thesupport member. The cantilever is formed by including slots 309 in theimplant mask used to define the support member. The slots form acantilever which can be induced to bend upward and have sufficientstiffness to increase the contact force between contacts. The length ofthe slots, for example is about ⅓-½ of the length of the support member.In one embodiment, the length of the slots is about 500 μm.

Where the first doped region is formed by implanting and/or diffusingdopants into the substrate, the depth of the second doped region shouldbe less than the depth of the first doped region to ensure correctformation of the support member by ECE.

After the second doped region is formed, the implant mask is removed bywet etching the oxide selective to silicon.

In one embodiment of the invention, an s-shaped support member isemployed to provide over-travel. To form the s-shaped support member,first and second stress layers that induce tensile and compressivestresses are deposited on surface of the substrate. The stress layerspreferably comprise high temperature formed materials. The hightemperature materials are formed by semiconductor processing such asthermal oxidation in either dry or wet ambient and different types ofchemical vapor deposition (CVD) processes such as low pressure CVD(LPCVD), high density CVD, or plasma enhanced CVD (PECVD). Suchmaterials are desirable as they have very stable electrical andmechanical properties. For example, the intrinsic stress characteristicsof the high temperature formed materials are very stable and areunaffected by the relatively lower temperature processes used to formother features of the relay. This results in a support member with astable bend or shape. Lower temperature formed materials that are stableenough could also be used.

Referring to FIG. 4, a first stress layer is deposited on the surface ofthe substrate. The first stress layer induces compressive stress on thesupport member. The compressive stress causes the support member to arcdownward.

In one embodiment, the first stress layer comprises silicon oxide(SiO₂). The thickness of the first stress layer induces the supportmember to bend as desired. Typically, the thickness of the SiO₂ is about4000-5000 Å. The thickness of the stress layer can be varied, dependingon design specifications such as over-travel and stiffness of thesupport member. In one embodiment, the SiO₂ is grown by thermaloxidation. The thermal oxidation can be performed in an oxygenatedambient. CVD techniques are also useful to form the first stress layer.

Alternatively, the first stress layer can comprise poly. The poly can bedoped or undoped. The poly can be deposited as poly or as amorphoussilicon which is subsequently recrystallized to form poly. Various CVDtechniques can be used to deposit the poly. Relatively stable materialsthat are formed at lower temperatures may also be used. Other materialsthat are stable enough and induce tensile stress on the support memberare also useful.

A second stress layer 472 is formed over the first stress layer. Thesecond stress layer induces a compressive stress on the support member.In one embodiment, the second stress layer comprises Si₃N₄. The Si₃N₄ isdeposited by, for example, LPCVD. Other techniques for forming thesecond stress layer are also useful. The thickness of the second stresslayer causes the support member to bend upward as desired. Typically,the thickness of the second stress layer is about 1000-2000 Å. Thethickness of the stress layer can vary, depending on designspecifications such as over-travel and stiffness of the support member.A material that is formed at lower temperatures and which is relativelystable, can also be used to form the second stress layer. Othermaterials that are stable enough and induce tensile stress on thesupport member are also useful.

An etch selectively removes unwanted portions of the secondstress-inducing layer, leaving a remaining portion in the first contactregion. The remaining portion of the second stress-inducing layer causesthe first contact region to arc in the opposite direction as the rest ofthe support member. In one embodiment, the etch also leaves portions ofthe second stress-inducing layer to completely cover the p-doped regionand the first contact region. The second stress layer that covers thep-doped region acts as an etch stop for the subsequent ECE process toensure that the other parts of the relay are protected from the ECEetchant.

Referring to FIG. 5, a conductive layer is formed on the substratesurface by conventional techniques such as, for example, sputtering,physical vapor deposition, or electroplating. The conductive layercomprises, for example, gold or a gold alloy such as gold-nickel(AuNi₅), gold palladium, or gold-cobalt. Other conductive materials,such as silver, or silver alloys, are also useful.

To ensure adhesion of the conductive layer to the surface of thesubstrate, an adhesion layer can be deposited on the substrate surfaceprior to the formation of the conductive layer. In one embodiment, theadhesion a layer comprises titanium. The titanium layer can also serveas a barrier layer to reduce inter-diffusion. Other materials thatpromote adhesion of the conductive material and support member, such aschromium, are also useful to serve as the adhesion layer. The adhesionis deposited by, for example, sputtering or evaporation. Otherdeposition techniques are also useful.

After formation of the conductive and adhesion layers, they arepatterned to form a first electrode 541 on the support member. In oneembodiment, the conductive layer is patterned, leaving the conductivelayer on the support member except the first contact region. To reducethe stress induced by the electrode on the support member, it should bethin. In one embodiment, the thickness of the electrode is about 75 nm.

A first contact 531 is formed in the first contact region. The contactcomprises a conductive material such as gold. Alloys comprising goldsuch as gold-palladium, gold-nickel, and gold-cobalt or alloyscomprising silver are also useful. Other materials that provide goodcontact characteristics can also be used. An adhesion layer such astitanium or chromium can be used to ensure adhesion of the contactmaterial to the support member. The contact and adhesion layer areformed using conventional techniques such as, for example, sputtering,physical vapor deposition, electroplating, or other techniques.

In one embodiment, a pad and a leadout which connects the pad to thecontact are also provided. The pad and leadout are, for example, formedfrom the same process as forming the contact. A readout region isprovided during the formation of the first electrode to accommodate theleadout. The readout region, for example, separates the first electrodeinto first and second subsections.

In one embodiment, the first contact is formed using electroplatingtechniques. Such techniques use a seed layer on which the contactmaterial is plated. The seed layer comprises a conductive material usedto form the contact. Other types of materials that facilitate plating ofthe contact material can also be used. Various techniques, such assputtering or evaporation, can be used to deposit the seed layer. Anadhesion layer, for example titanium or chromium, may be provided topromote adhesion of the seed layer.

The adhesion and seed layers (adhesion/seed layer), in one embodiment,also serve as the first electrode. To reduce the stress effects on thesupport member by the adhesion and seed layers, they should berelatively thin. To minimize the stress effects on the support member,the adhesion/seed layer should be as thin as possible. In oneembodiment, the adhesion layer is about 25 nm thick and the seed layeris about 50 nm thick, producing an adhesion/seed layer of about 75 nmthick.

In one embodiment, a mask is provided to selectively electroplate theconductive material in the first contact region to form the firstcontact. The mask, which may comprise resist, exposes the seed layer inthe region where the first contact is to be formed. The conductivematerial is plated onto the exposed portions of the seed layer to formthe first contact. The dimensions of the contact should be adequate tohandle the specified load current. The height, for example, is about 2.5μm.

The mask is removed after formation of the contact, exposing theseed/adhesion layer. An etch selectively removes portions of theseed/adhesion layer to form the first electrode 541. The etch, forexample, comprises an anisotropic etch such as a reactive ion etch(RIE). A etch mask is used to protect the portions of the seed/adhesionlayer that remain to serve as the first electrode.

In one embodiment, the etch mask for forming the first electrode neednot protect the contact. This results in a small amount of the surfaceof the contact and leadout being removed as the seed/adhesion layer ispatterned. However, since contact is much thicker than the seed/adhesionlayer, a sufficient amount should remain to serve as the contact.

The first electrode is electrically insulated from the contact. Asshown, the first electrode occupies the surface of the support memberexcept for the first contact region. This design maximizes the surfacearea of the electrode. Also the masks used to form the electrode andcontact can easily be modified to also include a pad and a leadoutconnecting the contact to the pad.

A dielectric layer can be provided underneath the lead out for thecontact. The dielectric layer provides electrical insulation between thelead out and the electrode, eliminating the need to pattern theelectrode into two subsections.

In an alternative embodiment, the conductive layer is electroplated ontothe seed/adhesion layer. Also, the conductive layer can be deposited onan adhesion layer by, for example, sputtering or physical vapordeposition or other deposition process that does not require the use ofa seed layer. The conductive layer is subsequently masked and etched toform the contact and, if applicable, the leadout and pad. Forming thecontact by masking and etching requires the deposition of an additionconductive layer to serve as the electrode.

Referring to FIG. 6, an over-travel region is formed to ensure that theover-travel of the s-shaped support member is not hindered. To form theover-travel region, a first sacrificial layer 630 is deposited on thesubstrate. The thickness of the sacrificial layer determines the depthof the over-travel region. The thickness is sufficient to accommodatethe over-travel of the support member. The thickness of the sacrificiallayer is, for example about 3-3.5 μm for a contact height of 2.5 μm.

The sacrificial layer comprises a material that can be etchedselectively to other relay materials. Preferably, the sacrificial layercomprises a material that can be etched quickly and easily withouteffectively removing other relay materials. In one embodiment, the firstsacrificial layer comprises copper. Aluminum, titanium, zirconium, iron,polyimide or other materials that can be etched selective to other relaymaterials are also useful. The use of SiO₂ as a sacrificial layer canalso be useful, particularly in the case of a nickel spring using Si₃N₄and poly as stress layers. The copper is deposited by, for example,physical vapor deposition or sputtering. Other deposition techniques,depending on the sacrificial material, are also useful.

Conventional mask and etch processes are used to pattern the sacrificiallayer to define the area of the over-travel region and to provide anopening 640 to the contact. The dimension of the over-travel regionshould be sufficient to ensure that the over-travel of the supportmember is not hindered. The opening 640 defines the portion of thesecond contact that comes into contact with the first contact when thecontacts are engaged.

In cases where the conductive and the sacrificial materials interact todegrade the contact characteristics of the conductive layer byinterdiffusion, a barrier layer can be provided between the two layers.Preferably, the barrier layer comprises a material that preventsinterdiffusion between the conductive and sacrificial materials and canbe removed selective to other relay materials. The barrier layer, forexample, comprises titanium, chromium, tungsten, or palladium.

A second sacrificial layer 631 is deposited over the surface. The secondsacrificial layer comprises a material that can be etched selectively toother relay materials. Preferably, the second sacrificial layercomprises a material that can be etched quickly and easily withoutremoving other relay materials. In one embodiment, the secondsacrificial layer comprises copper. Other materials that can be etchedselective to other relay materials are also useful. The copper isdeposited by, for example, physical vapor deposition or sputtering.Other deposition techniques, depending on the sacrificial material, arealso useful. Although not necessary, the first and second sacrificiallayers comprise the same material.

The second sacrificial layer defines the gap between the first andsecond electrodes. In one embodiment, the thickness of the secondsacrificial layer is about 0.5 μm to produce a 0.5 μm separation betweenthe electrodes. The second sacrificial layer is patterned byconventional mask and etch techniques to define the area of the cavity.

Referring to FIGS. 7, a dielectric layer 745 is deposited over thesubstrate to insulate the first electrode from the second electrode whenthe support member is moved upward. The thickness of the dielectriclayer should be sufficient to provide electrical insulation as specifiedby design parameters. Typically the thickness of the dielectric layer isabout 1 μm thick. Of course other thickness values can be used dependingon design specifications and dielectric characteristics of the material.

The dielectric layer should provide good step coverage over thesubstrate topography created by the different features thereon. Siliconoxide or other dielectric layers such as silicon nitride can be used toform the dielectric layer.

In one embodiment, the dielectric layer comprises a silicon-rich siliconnitride (Si₃N₄) dielectric layer. The Si₃N₄ is deposited by PECVD. Otherdeposition techniques, such as LPCVD, are also useful. The dielectriclayer is patterned, forming a contact opening to the first contact.Conventional masking and etching processes remove portions of thedielectric material to expose the contact opening 640.

The second electrode and second contact of the relay are formed. Ifnecessary, a barrier layer can be provided on the surface of the secondsacrificial layer prior to the formation of the contact and electrode toprevent interdiffusion between the contact and sacrificial materials.Preferably, the barrier layer comprises a material that can beselectively removed to other relay materials. The barrier layer, forexample, comprises titanium, chromium, tungsten, or palladium. Otherbarrier materials which prevent interdiffusion between the contact a andsacrificial materials are also useful.

In one embodiment, the electrode and contact are formed byelectroplating techniques as previously described. A seed layer topromote plating of the conductive material used to form the contact andelectrode is formed by, for example, sputtering or other techniques onthe substrate surface, covering the dielectric layer. In one embodiment,the seed layer comprises gold. Other materials that promote plating ofthe contact and electrode materials are also useful.

A conductive material is electroplated on the seed layer. The conductivematerial serves as the electrode and contact. In one embodiment, theconductive material comprises gold or a gold alloy such asgold-palladium, gold nickel (AuNi₅), or gold-cobalt. Other metals oralloys, such as silver or silver alloys, are also useful. Othermaterials that provide good contact characteristics can also be used.The thickness of the conductive material and seed layer, for example, isabout 2.5 μm.

An adhesion layer is provided to promote adhesion of the contact andelectrode to the upper portion of the relay body. The adhesion layercomprises, in one embodiment, titanium. An adhesion layer comprisingchromium or a material that promotes adhesion of the conductive materialto the upper portion of the relay is also useful. The adhesion layer canbe deposited by sputtering, evaporation, plating or other techniques.The seed layer, conductive layer, and adhesion layers are patternedusing conventional mask and etch processes to form the second electrode740 and second contact 730. The mask and etch processes also formreadouts and pads.

In an alternative embodiment, the conductive layer is deposited bysputtering, physical vapor deposition, or other deposition processeswhich do not require the use of a seed layer.

In yet another alternative embodiment, a mask layer is used toselectively plate the conductive material on the seed layer to form thesecond electrode and second contact. The mask is removed after theelectrode and contact are formed. An adhesion layer is deposited andpatterned to form the adhesion layer over the second contact and secondelectrode.

Referring to FIG. 8, a cap 805 is formed. The cap forms the upperportion of the relay, supporting the second electrode and secondcontact. The cap comprises a material sufficent to support the contactand electrode. In one embodiment, the cap comprises nickel or a nickelalloy such as NiFe. Materials such as gold, plastic, epoxy, or othersmaterials that can adequately support the relay components as needed canbe used.

If a conductive material is used to form the cap, a dielectric layer 880is formed over the surface of the substrate prior the formation of thecap. The dielectric layer serves to insulate the cap from the contactsand electrodes to prevent shorting of the relay components. Variousdielectrics can be used to form the dielectric layer. In one embodiment,the dielectric comprises SiO₂ formed by PECVD. Other techniques to formthe dielectric layer are also useful. The thickness of dielectric layeris sufficient to satisfy design specifications. The dielectric layer is,for example, about 1 μm thick. Of course, the thickness can be varieddepending on the design specification and the dielectric material used.

The dielectric layer is patterned using conventional techniques to coverthe region of the substrate on which the cap is formed. The pads to thecontacts and electrodes are exposed to allow access thereto.

In one embodiment, the nickel cap is formed by electroplating. Anadhesion layer is formed over the substrate to promote adhesion betweenthe cap materials and the substrate. The adhesion layer comprises, forexample, titanium. Other materials such as chromium or materials thatpromote adhesion are also useful. The adhesion layer is about 25 nm. Aseed layer is formed over the substrate to facilitate plating of the capmaterial. The seed layer comprises, for example, nickel of about 50 μmthick. The nickel cap layer is then electroplated onto the seed layer.The thickness of the cap is, for example, about 5-10 μm. The cap layeralong with the adhesion and seed layers are patterned to form the cap805. The pads to the contacts and electrodes are exposed to allow accessthereto.

Alternatively, a mask layer is formed to selectively plate the cap layerin the cap region. The mask is removed, exposing the seed and adhesionlayer. The exposed seed and adhesion layers are removed.

The backside of the substrate is masked, exposing the region of thesubstrate to be removed to form the cantilever support member. Thesubstrate is etched using ECE techniques. The etch removes the p-dopedregions of the substrate, including the area surrounded by n-dopedregions. The ECE stops or passivates on the n-doped regions and thenitride. A etch then removes the nitride layer, exposing the sacrificiallayers. The etch, which for example comprises a dry etch, employschemistry that etches nitride selective to silicon. A wet etch is thenemployed to etch the sacrificial layers and barrier layers, separatingthe support member from the upper portion of the relay body.

In another embodiment, the first contact is not provided with a leadout. Instead, the first contact serves as a bridging contact toelectrically couple first and second contacts located in the secondcontact region in the upper portion of the relay body.

Referring to FIG. 9, a substrate 301 having been processed to include apatterned first sacrificial layer 930 is shown. First and second contactopenings 940 and 941 are formed, exposing the surface of the firstcontact beneath. The process continues, providing a second sacrificiallayer and dielectric layer as previously described.

Referring to FIG. 10, electrode 140 and second and third contacts 150and 151 are formed. Contact pads and readouts can also be provided forthe electrode and the contacts. The contacts and electrode are formed byelectroplating techniques. Other techniques, such as depositing aconducting layer and patterning it to form the contacts and electrodes,are also useful. The process continues as previously described tocomplete the relay.

In an alternative embodiment of the invention, the support member isdefined by removing portions of the substrate. Referring to FIG. 11, asubstrate 101 is provided. The substrate is, for example, a siliconwafer. Other types of substrates are also useful. The substratecomprises a first doped region, such as a p-doped region. The firstdoped region can be either part of the substrate or formed. A seconddoped region 107, such as an n-doped region, is provided on the surfaceof the substrate. The depth of the second doped region defines thethickness of the support member.

As the support member is defined by etching into the surface of thesubstrate, it is not necessary to provide a heavily doped region. Anetch mask is formed on the surface of the substrate and patterned toexpose portions of the substrate. The pattern of the mask defines theshape of the support member.

The exposed portions of the substrate are removed by an anisotropic etchsuch as RIE, forming a trench 180 on the surface of the substrate. Thedepth of the trench is deeper than the n-doped region to ensure correctformation of the support member by the subsequent ECE etch as describedin FIG. 8.

A barrier layer 190 for the subsequent ECE etch as described in FIG. 8is formed on the substrate, covering the surface and lining the trench.In one embodiment, the ECE etch barrier comprises Si₃N₄. Other materialsthat is not etched by the ECE etch chemistry can also be used.

Referring to FIG. 12, a plug 196 is provided over the trench 180 toenable subsequent processing. The plug comprises, in one embodiment,aluminum. The plug is formed by sputtering aluminum on the substrate.Other deposition techniques are also useful.

Alternatively, the plug material comprises silicate glass. In oneembodiment, the plug material comprises doped silicate glass. The dopedsilicate is, for example borophosphosilicate glass (BPSG). Materialsthat can fill the trenches are also useful. Other doped silicate glass,such as phosphosilicate glass (PSG) and borosilicate glass (BSG), orundoped'silicate glass can also be used. If the plug material used isunaffected by the etch ECE chemistry, a separate ECE barrier layer isnot necessary since the plug can serve as the ECE barrier.

The process for forming-the relay continues as described in FIG. 4.

In another embodiment, a dual support member is provided in the relay asdescribed in FIG. 2 Fabricating the dual support member relay is similarto the process already described except a second support member isdefined during the process of defining the support member.

To form the over-travel region, an additional sacrificial layer is used.In one embodiment, the dual support member relay employs the use ofthree sacrificial layers. For example, the first sacrificial layerdefines the gap between the first and second contacts, the secondsacrificial layer defines the over-travel region, and the thirdsacrificial layer defines the gap between the first and secondelectrodes.

While the invention has been particularly shown and described withreference to various embodiments, it will be recognized by those skilledin the art that modifications and changes may be made to the presentinvention without departing from its scope. The scope of the inventionshould therefore be determined not with reference to the abovedescription but with reference to the appended claims along with theirfull scope of equivalents.

What is claimed is:
 1. A microstructure relay comprising: a bodyincluding upper and lower portions, wherein the lower portion is formedfrom a substrate and the upper portion is formed on the substrate toavoid bonding of the lower portion to the upper portion; a supportmember having a first end fixed to the body to form a cantilever,wherein an upper surface of the support member and a lower surface ofthe upper portion of the body forms a cavity; and a first contact regionlocated on the upper surface at a second end of the support member, thefirst Contact region comprising a first contact the pivoting the supportmember toward the lower surface causes the first contact to beelectrically coupled to a counter contact, wherein the support membercomprises an s-shape to provide for over-travel when the support memberis pivoted toward the lower surface.
 2. The microstructure relay ofclaim 1 wherein the s-shape support member comprises first and secondstress layers, the first stress layer inducing a compressive stress onthe support member to cause it to bend away from the low surface, andthe second stress layer inducing a tensile stress on the first contactregion to cause the first contact region to bend toward the lowersurface.
 3. The microstructure relay of claim 2 wherein the bend of thefirst contact region toward the lower surface defines an over-travel. 4.The microstructure relay of claim 3 further comprising an over-travelregion in the lower surface, the over-travel region accommodating thebend of the fist contact region to prevent the over-travel from beingobstructed.
 5. The microstructure relay of claim 4 wherein the supportmember comprises silicon.
 6. The microstructure relay of claim 5 whereinthe first stress layer comprises silicon oxide.
 7. The microstructurerelay of claim 6 wherein the second stress layer comprises siliconnitride.
 8. The microstructure relay of claim 7 wherein the lowerportion of the body comprises silicon.
 9. The microstructure relay ofclaim 8 wherein the upper portion comprises nickel.
 10. Themicrostructure relay of claim 9 further comprising a dielectric layerinsulating the upper portion of the body from the second contact andsecond electrode.
 11. The microstructure relay of claim 4 wherein thesupport member comprises nickel.
 12. The microstructure relay of claim11 wherein the first stress-inducing layer comprises silicon oxide andthe second stress-inducing layer comprises polysilicon.
 13. Themicrostructure relay of claim 12 wherein the polysilicon comprises dopedpolysilicon.
 14. The microstructure relay of claim 13 further comprisesa compensation layer on a surface of the support member opposite theupper surface, the compensation layer having a thermal coefficient ofexpansion (TCE) similar in magnitude to a TCE of the firststress-inducing layer.
 15. The microstructure relay of claim 14 whereinthe compensation layer and the first stress layer have intrinsicstresses and the intrinsic stress of the compensation layer is lowerthan the intrinsic stress of the first stress layer to reduce theinfluence of the compensation layer on the support member.
 16. Amicrostructure relay comprising: a body including upper and lowerportions, wherein the lower portion is formed from a substrate and theupper portion is formed on the substrate to avoid bonding of the lowerportion to the upper portion; a support member having a first end fixedto the body to form a cantilever, wherein an upper surface of thesupport member and a lower surface of the upper portion of the bodyforms a cavity; a first contact region located on the upper surface at asecond end of the support member, the first contact region comprising afirst contact, wherein pivoting the support member toward the lowersurface causes the first contact to be electrically coupled to a countercontact; and a stress-inducing layer on the upper surfaces of the fastand second support members, the stress layer inducing a compressivestress on support member to cause it to bend away from the lower surfaceupper portion of the body.
 17. The microstructure relay of claim 16wherein the support member comprises silicon.
 18. The microstructurerelay of claim 17 wherein the stress-inducing layer comprises siliconoxide.
 19. The microstructure relay of claim 18 wherein the secondsupport member is shorter than the first support member.
 20. Themicrostructure relay of claim 19 wherein an over-travel is defined bythe second support member.
 21. The microstructure relay of claim 20further comprises an over-travel region on the second support member toensure the over-travel is not obstructed as the first support member ispivoted toward the lower surface.
 22. A micro-relay comprising: a bodyincluding upper and lower portions, a support member supported at afirst end by the body to form a cantilever, where a major surface of thesupport member and a lower surface of the upper portion of the bodyforms a cavity; and a first contact region located on the major surfaceat a second end of the support member, the first contact regioncomprising a first contact, the support member comprising an s-shape,wherein a body of the support member bends in a direction away from thesurface of the upper portion of the body and the first contact regionbeads in a direction toward the surface of the upper portion of thebody, the s-shaped support member, when pivoted toward the lowersurface, causes the first contact to be electrically coupled to acounter contact.
 23. The microstructure relay of claim 22 wherein thesupport member is pivoted toward the lower surface by electrostaticforce, the electrostatic force generated by applying a voltage potentialto a first electrode located on the upper surface and a second electrodelocated on the lower surface.
 24. The microstructure relay of claim 23further comprises a second contact region on the lower surface, thesecond contact region comprising the second contact.
 25. Themicrostructure relay of claim 24 wherein the s-shape support membercomprises first and second stress layers, the first stress layerinducing a compressive stress on the support member to cause it to bendaway from the lower surface, and the second stress layer inducing atensile stress on the first contact region to cause the fist contactregion to bend toward the lower surface.
 26. The microstructure relay ofclaim 25 wherein the bend of the first contact region toward the lowersurface defines an over-travel.
 27. The microstructure relay of claim 26further comprising an over-travel region in the lower surface, theover-travel region accommodating the bend of the fast contact region toprevent the over-travel from being obstructed.
 28. The microstructurerelay of claim 27 wherein the support member comprises silicon.
 29. Themicrostructure relay of claim 28 wherein the first stress layercomprises silicon oxide.
 30. The microstructure relay of claim 29wherein the second stress layer comprises silicon nitride.
 31. Themicrostructure relay of claim 30 wherein the lower portion of the bodycomprises silicon.
 32. The microstructure relay of claim 31 wherein theupper portion comprises nickel.
 33. The microstructure relay of claim 32further comprising a dielectric layer insulating the upper portion ofthe body from the second contact and second electrode.
 34. Themicrostructure relay of claim 27 wherein the support member comprisesnickel.
 35. The microstructure relay of claim 34 wherein the firststress-inducing layer comprises silicon oxide and the secondstress-inducing layer comprises polysilicon.
 36. The microstructurerelay of claim 35 wherein the polysilicon comprises doped polysilicon.37. The microstructure relay of claim 36 further comprises acompensation layer on a surface of the support member opposite the uppersurface, the compensation layer having a thermal coefficient ofexpansion (TCE) similar in magnitude to a TCE of the firststress-inducing layer.
 38. The microstructure relay of claim 37 whereinthe compensation layer and the first stress layer have intrinsicstresses and the intrinsic stress of the compensation layer is lowerthan the intrinsic stress of the first stress layer to reduce theinfluence of the compensation layer on the support member.
 39. Themicrostructure relay of claim 23 further comprises a second supportmember, the second support member having a first end fixed to the bodyand the counter contact is supported at a second end on an upper surfaceof the second support member, wherein the support member is pivotedtoward the lower surface by electrostatic force, the electrostatic forcegenerated by applying a voltage potential to the first and secondelectrodes, the first electrode is located on the upper surface and thesecond electrode is located on the lower surface.
 40. The microstructurerelay of claim 39 further comprises a stress-inducing layer on the uppersurfaces of the first and second support members, the stress layerinducing a compressive s on support member to cause it to bend away fromthe lower surface upper portion of the body.
 41. The microstructurerelay of claim 40 wherein the support member comprises silicon.
 42. Themicrostructure relay of claim 41 wherein the stress-inducing layercomprises silicon oxide.
 43. The microstructure relay of claim 42wherein the second support member is shorter than the first supportmember.
 44. The microstructure relay of claim 43 wherein an over-travelis defined by the second support member.
 45. The microstructure relay ofclaim 44 further comprises an over-travel region on the second supportmember to ensure the over-travel is not obstructed as the first supportmember is pivoted toward the lower surface.